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Quantum dot (QD) emits light of characteristic wavelength which depends on the size of the QD particles, and thus the quality control of QD requires accurate determination of its size distribution. Field-flow fractionation (FFF) is a separation technique that is well suited for the characterization of colloidal particles. In this study, CdS-QD particles were synthesized by a simple one-step γ-ray irradiation. Then asymmetrical flow FFF (AsFlFFF) and sedimentation FFF (SdFFF) were tested as tools for characterization of the particles. The single crystallite size of CdS-QD was measured to be about 4 nm by X-ray diffraction (XRD), UV-VIS absorption spectroscopy, and transmission electron microscopy (TEM). TEM images indicate that the particles were agglomerated to form larger secondary particles (~ 110 nm). Effects of the various experimental parameters of FFF including the type of dispersing agent, the ionic strength of the carrier liquid, and strength of external field were investigated. It was found that, among the dispersing agents tested, a mixture of anionic and nonionic surfactants tends to give better elution of CdS particles than anionic or nonionic surfactants. Results suggest that FFF can provide some advantages over dynamic light scattering (DLS) or TEM for size characterization of CdS particles, and with a proper optimization, FFF (AsFlFFF or SdFFF) could become a useful tool for stability study as well as size analysis of nanoparticles such as the CdS particles synthesized in this study.

Non-enzymatic biosensors employing multi-walled carbon nanotube (MWNT) with highly dispersed Pt-M (M = Ru, Sn, and Au) nanoparticles (Pt-M@MWNT catalysts) were fabricated by radiolytic deposition. The Pt-M nanoparticles on the MWNTs were characterized by transmittance electron microscopy, elemental analysis, and X-ray diffraction. They were found to be well-dispersed and to exhibit alloy properties on the MWNT support. Electrochemical testing showed that these non-enzymatic biosensors had larger currents (mA) than that of a bare glassy carbon (GC) electrode and one modified with MWNTs. The sensitivity (μA mM-1), linear range (mM), and detection limit (mM) (S/N = 3) of the glucose biosensor with the Pt-Ru, Pt-Sn and Pt-Au catalysts in PBS electrolyte were determined, respectively. The experimental results show that such biosensors can be applied to glucose detection in food chemistry field.

An ECL sensor was fabricated by immobilization of a tris(2,2'-bipyridyl)ruthenium (II) complex (Ru(bpy)3(2+)) to an amine group-modified GC electrode (NH2-GC electrode). Here, the NH2-GC electrode was prepared by electrochemical reduction of a nitro group-modified GC electrode in 0.1 M KCl ethanol solution under H2 gas, which was followed by electrochemical grafting of 4-nitrophenyl diazonium salts in 0.1 M NBu4BF4 acetonitrile solution onto the GC electrode. The prepared ECL sensor was successfully confirmed via cyclic voltammetry, contact angle, scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and ECL spectrometry. The contact angle for the surface of the GC electrode, NO2-GC electrode, and NH2-GC electrod was 88.4 degrees, 67.4 degrees, and 52.4 degrees, respectively. The stability of the ECL sensor was investigated under continuous cyclic potential scanning for 55 cycles and the ECL intensity remained at 55%. The prepared ECL electrode can be expected to immobilize enzymes for preparation of the ECL biosensor to detect target molecules.

Vinyl copolymer–clay nanocomposites were prepared by γ-irradiation-initiated radical polymerization using a mixture of styrene (St) and divinyl benzene (DVB) in the presence of reactive organic montmorillonite clay (OMMT) in methanol at room temperature. Reactive OMMT was synthesized by a cation exchange reaction of Na + -MMT and 1-[(4-ethylphenyl)methyl]-3-butyl-imidazolium chloride as a reactive organic modifier in an aqueous solution. The microstructures of the nanocomposites were confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The thermal stability was examined by thermo gravimetric analysis (TGA). As a result, the reactive OMMT was a good additive material for preparing vinyl copolymer–clay nanocomposites.

Pt–M@FP-MWNT catalysts (M = Ru, Ni, Co, Sn, and Au) were prepared by one-step γ-ray irradiation. Two different types of functional polymers (FP), such as poly(vinylphenyl boronic acid) (PVPBAc) and poly(vinylpyrorridone) (PVP), were used as anchoring agents, when Pt–M nanoparticles were deposited on the multi-walled carbon nanotube (MWNT) using γ-ray irradiation in aqueous solution at room temperature. The obtained Pt–M@FP-MWNT catalysts were then characterized by XRD, TEM, and elemental analysis. The catalytic efficiency of the Pt–M@FP-MWNT catalysts was examined for CO stripping and MeOH oxidation for use in a direct methanol fuel cell (DMFC). The catalytic efficiency of the Pt–M@FP-MWNT catalyst for MeOH oxidation follows this order: Pt–Sn@FP-MWNT > Pt–Co@FP-MWNT > Pt–Ru@FP-MWNT > Pt–Au@FP-MWNT > Pt–Ni@FP-MWNT catalysts. The CO adsorption capacity of the Pt–M@FP-MWNT catalyst for CO stripping is as follows: Pt–Ru@FP-MWNT > Pt–Sn@FP-MWNT > Pt–Au@FP-MWNT > Pt–Co@FP-MWNT > Pt–Ni@FP-MWNT catalyst.

A multi-walled carbon nanotube (MWNT) support with dual properties, an ionic property via tetra-amine and unpaired electrons via tri-amine, was prepared by radiation-induced graft polymerization of glycidyl methacrylate (GMA) and the subsequent amination of its epoxy group. The electrochemical microbial biosensor (EMB) was then fabricated by immobilization of a microbe (Alkaligenes spp.) onto the dual property-modified electrode, which was prepared with the mixture of the MWNT support and a solution on a glass carbon (GC) electrode surface by a hand-casting method. The sensing range of the prepared EMB for phenol in a phosphate buffer solution was 0.005~7.0 mM. The total concentration of phenolic compounds in a commercial red wine was also determined using the EMB.

Asymmetrical flow field-flow fractionation (AsFlFFF) was coupled online with multiangle light scattering (MALS) to study the changes in the molecular weight and the size distribution of the corn starch during carboxymethylation. A corn starch was derivatized with sodium chloroacetate in alcoholic medium under alkaline condition to produce carboxymethyl starches (CMS) having various degrees of substitution (DS). The change in thermal characteristics and granule structure of the native corn starch and CMS were compared using Thermogravimetric analysis and scanning electron microscope. The ionic strength of the carrier liquid (water with 0.02% NaN(3)) was optimized by adding 50mM NaNO(3) to minimize the interactions among the starch molecules and between the starch molecules and the AsFlFFF membrane. A field-programmed AsFlFFF allowed determination of the molecular weight distribution (MWD) of starches within about 25min. It was found that carboxymethylation of starch results in reduction in the molecular weight due to molecular degradation by the alkaline treatment. The weight-average molecular weight (M(w)) was reduced down to about 4.4x10(5) from about 7.2x10(6) when DS was 0.14. It seems AsFlFFF coupled with MALS (AsFlFFF/MALS) is a useful tool for monitoring the changes taking place in the molecular weight and the size of starch during derivatization.

The split-flow thin cell fractionation (SF) is a useful tool for separating colloidal particles or macromolecules into two or more fractions in a preparative scale. In a conventional design, the SF channel is equipped with flow stream-splitters at the inlet and the outlet of the channel, which may cause deterioration of the resolution due to the disturbance in the flow stream by the imperfection of the splitter geometry. In this study, a new splitter-less SF channel was implemented, which was designed to operate only in the full-feed depletion (FFD) mode (FFD-SF). Without the splitters, it was possible to make the channel much larger than conventional ones (about 25 times larger in the channel volume), and thus obtain a much higher sample throughput ( TP , amount of the sample that can be processed in a unit time period). The new splitter-less FFD-SF system was tested and optimized using polyurethane (PU) latex spheres, and then applied successfully to a large scale separation of sea sediment. A series of three steps of FFD-SF operations (with each step repeated, and there were 6 steps in total) yielded separation of the sea sediment into four fractions having diameter ranges of larger than 10 µm, between 5 and 10 µm, between 2 and 5 µm, and smaller than 2 µm. TP of the three FFD-SF operations were 37.3, 22.1, and 17.9 kg/h, and the fractionation efficiencies ( FE ) of the four size fractions were 80.5, 73.7, 79.1 and 86.1%. Results suggest the new splitter-less FFD-SF system could be a useful tool for large scale separation of complex particulates such as environmental particles.

A cation-exchange nanofiber poly(vinylidene fluoride) (PVdF) membrane was prepared by a radiation-induced graft polymerization (RIGP) of sodium styrene sulfonate (NaSS) in the presence of the polymerizable access agents in methanol solution. The used polymerizable access agents include styrene, acrylic acid, and vinyl pyrrolidone. The anion-exchange nanofiber PVdF membrane was also prepared by RIGP of glycidyl methacrylate (GMA) and its subsequent chemical modification. The successful preparations of cation- and anion-exchange PVdF membranes were confirmed via SEM, XPS and thermal analysis. The content of the grafting yield, ion-exchange group, and water uptake was in the range of 30.0~32.3%, 2.81~3.01 mmol/g and 66.6~147%, respectively. The proton conductivity at 20 was in the range of 0.020~0.053 S/cm. From the result, the prepared ionexchange PVdF membrane can be used as a separator in battery cells.

Polyamidoamine (PAMAM) dendrimers have an amine surface and an ethylenediamine core and are of great interest in various applications such as in drug delivery. Physiochemical properties of PAMAM dendrimers vary with pH. At neutral to basic pH, PAMAM dendrimers are either weakly charged or uncharged and tend to adsorb on to the neutral packing material, making chromatographic separation of the dendrimers difficult. Asymmetrical flow field-flow fractionation (AsFlFFF) was tested as an alternative to the chromatographic techniques for separation of the PAMAM dendrimers. AsFlFFF provided generation-based separation of the dendrimers even at neutral and basic pH. The elution time increased gradually as the generation number (and thus the size) increased. Separation of impurities such as generational or missing-arm impurities and aggregates from the main population was also achieved. Electrostatic and hydrophobic interactions (e.g., repulsive elecrostatic interaction among the dendrimer molecules or attractive hydrophobic interaction between the dendrimer molecules and the membrane) may result in an inaccurate size measurement. Careful optimization of experimental conditions such as the flow rate, pH, and the salt concentration may be required to minimize the interactions with the membrane. AsFlFFF was also tested for a study on the interaction between the PAMAM dendrimers and proteins. AsFlFFF was able to show the growth in the size of bovine serum albumin (BSA) when BSA is mixed with increasing amounts of PAMAM dendrimers. Results suggest that, with proper optimization, AsFlFFF could become a useful tool for separation and characterization of large charged molecules such as PAMAM dendrimers.

Split-flow thin cell (SPLITT) fractionation (SF) provides separation of colloidal particles or macromolecules into two fractions. A gravitational SF (GSF) system was constructed and its applicability was tested for removal of aggregates from mass-produced polymethyl methacrylate (PMMA) latex beads. The full-feed depletion (FFD) mode of GSF (FFD-GSF) was found to be a simpler alternative to the conventional mode for removal of the aggregates. Unlike in the conventional mode, where two inlets are used for feeding of the sample suspension and the carrier liquid respectively, only one inlet (for the sample feeding) is used in the FFD mode, allowing easier control of the flow rate. Also the sample suspension is not diluted during FFD mode operation. Aggregated particles were found only in one of the two fractions, allowing removal of the aggregates. The sample was continuously fed into the GSF system, showing potential application to a large quantity operation for removal of the PMMA aggregates.

A PtRu@TiO2-hollow nanocomposite for the detection of biomolecules was synthesized by chemical reduction. First, poly(styrene-co-vinylphenylboronic acid), PSB, was prepared as a template (approximately 250 nm) by surfactant-free emulsion polymerization. Second, PSB/TiO2 core-shell spheres were prepared by sol-gel reaction. Finally, TiO2 hollow spheres (TiO2-H) were then formed after removing the PSB template by calcination at 450 degrees C under air atmosphere. To prepare the electrocatalyst, PtRu nanoparticles (NPs) were deposited onto the TiO2-H surface by chemical reduction. The prepared PtRu@TiO2-H nanocomposite was characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and elemental analysis. A non-enzymatic sensor was fabricated by depositing the as-prepared PtRu@TiO2-H nanocomposite on the surface of a glassy carbon electrode (GCE), which was prepared by a hand casting method with Nafion solution as a binder. The sensor was tested as a biomolecule sensor, especially for the detection of glucose and dopamine. The cyclic voltammograms (CV) obtained during the oxidation studies revealed that the PtRu@TiO2-H nanocomposite showed better catalytic function toward the oxidation of dopamine. The sensing range of the non-enzymatic sensor for glucose was 5.0-100 mM in a phosphate buffer. The results demonstrated the potential usefulness of this bimetallic@TiO2-H bifunctional catalyst for biosensor applications.

This paper describes the electrocatalytic activity for CO, MeOH, and EtOH oxidation on the surface of Pt-Ru nanoparticles supported by metal oxide (Nb-TiO2-H) prepared for use in a fuel cell. To prepare Nb-TiO2-supported Pt-Ru nanoparticles, first, the Nb-TiO2supports were prepared by sol-gel reaction of titanium tetraisopropoxide with a small amount of the niobium ethoxide in polystyrene (PS) colloids. Second, Pt-Ru nanoparticles were then deposited by chemical reduction of the Pt4+and Ru3+ions onto Nb-TiO2supports (Pt-Ru@Nb-TiO2-CS). Nb element was used to reduce electrical resistance to facilitate electron transport during the electrochemical reactions on a fuel cell electrode. Finally, the Pt-Ru@Nb-TiO2-H catalysts were formed by the removal of core-polystyrene ball from Pt-Ru@TiO2-CS at500∘C. The successfully prepared Pt-Ru electrocatalysts were confirmed via TEM, XPS, and ICP analysis. The electrocatalytic efficiency of Pt-Ru nanoparticles was evaluated via CO, MeOH, and EtOH oxidation for use in a direct methanol fuel cell (DMFC). As a result, the Pt-Ru@Nb-TiO2-H electrodes showed high electrocatalytic activity for the electrooxidation of CO, MeOH, and EtOH.

Pt-Ru catalysts based on functional polymer-grafted MWNT (Pt-Ru@FP-MWNT) were prepared by radiolytic deposition of Pt-Ru nanoparticles on functional polymer-grafted multiwalled carbon nanotube (FP-MWNT). Three different types of functional polymers, poly(acrylic acid) (PAAc), poly(methacrylic acid) (PMAc), and poly(vinylphenyl boronic acid) (PVPBAc), were grafted on the MWNT surface by radiation-induced graft polymerization (RIGP). Then, Pt-Ru nanoparticles were deposited onto the FP-MWNT supports by the reduction of metal ions usingγ-irradiation to obtain Pt-Ru@FP-MWNT catalysts. The Pt-Ru@FP-MWNT catalysts were then characterized by XRD, XPS, TEM ,and elemental analysis. The catalytic efficiency of Pt-Ru@FP-MWNT catalyst was examined for CO stripping and MeOH oxidation for use in a direct methanol fuel cell (DMFC). The Pt-Ru@PVPBAc-MWNT catalyst shows enhanced activity for electro-oxidation of CO and MeOH oxidation over that of the commercial E-TEK catalyst.

The γ-ray irradiation polymerization is beneficial technology that is environmentally friendly and energy efficient in the preparation of polymer nanocomposites. Two active species such as a free radical and a hydrated electron generated during γ-ray irradiation are used in preparing polymer-clay nanocomposites, polymer-metal nanocomposites, and polymer-carbon nanotube at room temperature and under ambient pressure. Various polymer-clay nanocomposites using γ-ray polymerization of the desired monomers can be prepared in a one step process. The prepared polymer-clay nanocomposites have the improved mechanical properties, enhanced thermal stability, and reducing gas permeability. Precious metals have been studied most extensively among polymer-metal nanocomposites and used as catalysts, in sensors, photochromic and electrochromic devices, and recording materials. Various functional groups can be introduced on the CNT surface by γ-ray irradiation polymerization as a one-step process. The polymer-CNT nanocomposites can be used as supports to immobilize biomolecules in the biosensor. This radiolytic preparation of polymer nanocomposites is expected to have actual applications in industrial fields because this method is very simple, has low cost, and can be produced at room temperature, with or without solvents.